Stormwater treatment apparatus

ABSTRACT

A liquid purification and separation apparatus for separation of pollutants in stormwater runoff is disclosed. This apparatus utilizes gravitational separation and tortuosity, resulting from a plurality of baffles both perpendicular to and oblique to the primary water flow direction, to trap substances less-dense and more-dense than water. The apparatus features improved resistance to pollutant remobilization through treatment of water volume rather than flow rates, using vertically stacked water columns of varying depths to settle small particles. An overflow structure diverts excessive liquid without interfering with purification and separation, and can be placed integrally within or external to the apparatus receptacle.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/487,097, filed Jan. 19, 2000, entitled“Stormwater Treatment Apparatus” and incorporated in its entirety hereinby reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] Apparatus for treatment of stormwater runoff throughvolume-control-based detention and minimization of pollutantremobilization.

[0004] 2. Description of the Related Art

[0005] This invention relates generally to liquid purification andseparation and, more specifically, to an apparatus for separation ofpollutants in urban stormwater runoff from the runoff water. Thisapparatus utilizes gravitational separation and tortuosity, resultingfrom a plurality of baffles both perpendicular to and oblique to theprimary water flow direction, to trap substances less-dense andmore-dense than water. This invention is differentiated from prior artby improved resistance to pollutant remobilization, resulting from aniterative experimental hydraulic design process. In addition, thisinvention provides a degree of retention through volume-control thatexceeds that provided by existing gravitational, sub-surface, stormwatertreatment systems.

[0006] Impacts of stormwater runoff on receiving environments have beendocumented extensively in engineering and scientific literature. Section402 of the Federal Clean Water Act (CWA) regulates stormwater dischargesthrough the National Pollutant Discharge Elimination System (NPDES).Treatment of stormwater runoff using best management practices (BMPs) isa typical requirement of state and local regulations, as well. In the1990s, there has been growing interest in ‘ultra-urban/space limited’BMP's, such as sand filters, water quality inlets, and, reservoir/vaulttype of structures. Space constraints, high property values, soilconditions, and the proximity of other building foundations oftenpreclude the use of conventional, space-intensive stormwater BMP's suchas detention ponds. For in-fill construction or redevelopment inbuilt-up urban areas, where pollutant loads from urban runoff areusually the greatest, unconventional stormwater treatment technologiesmay be necessary.

[0007] Vault-type treatment technologies have been widely used forstormwater treatment in urban areas; however, the effectiveness of thesedevices for removal of suspended solids and oil and grease has been onlymarginal. A great weakness of these types of devices has been that largestorm events tend to flush out the system, thereby releasing pollutantsthat were previously removed.

[0008] Prior art in the field of this invention of which the applicantis aware includes the following:

[0009] U.S. Pat. No. 4,127,488, Bell, J. A. et al., November 1978,Method and apparatus for separating solids from liquids.

[0010] U.S. Pat. No. 4,136,010, Pilie, R. J. et al., January 1979, Catchbasin interceptor.

[0011] U.S. Pat. No. 4,328,101, Broden, C. V., May 1982, Device forseparating particulate matter from a fluid.

[0012] U.S. Pat. No. 4,363,731, Filippi, R., December 1982, Device forregulating the flow of waste waters.

[0013] U.S. Pat. No. 4,383,922, Beard, H. J., May 1983, Waste waterclarifier.

[0014] U.S. Pat. No. 4,983,295, Lamb, T. J. et al., January 1991,Separator.

[0015] U.S. Pat. No. 4,985,148, Monteith, J. G., January 1991, Improvedseparator tank construction.

[0016] U.S. Pat. No. 5,004,534, Buzzelli, V., April 1991, Catch basin.

[0017] U.S. Pat. No. 5,186,821, Murphy, D. T., February 1993, Wastewatertreatment process with cooperating velocity equalization, aeration, anddecanting means.

[0018] U.S. Pat. No. 5,342,144, McCarthy, E. J., August 1994, Stormwatercontrol system.

[0019] U.S. Pat. No. 5,520,825, Rice, W. M., May 1996, Oil-waterseparator.

[0020] U.S. Pat. No. 5,536,409, Dunkers, K. R., July 1996, Watertreatment system.

[0021] U.S. Pat. No. 5,637,233, Earrusso, P. J., June 1997, Method andapparatus for separating grease from water.

[0022] U.S. Pat. No. 5,679,258, Petersen, R. N., October 1997, Mixedimmiscible liquids collection, separation, and disposal method andsystem.

[0023] U.S. Pat. No. 5,759,415, Adams, T., June 1998, Method andapparatus for separating floating and non-floating particulate fromrainwater drainage.

[0024] U.S. Pat. No. 5,788,848, Blanche, P. et al., August 1998,Apparatus and methods for separating solids from flowing liquids orgases.

[0025] U.S. Pat. No. RE30,793, Dunkers, K. R., November 1981, Apparatusfor water treatment.

[0026] In addition to the patents listed above, a number of inventionsin the general field of stormwater treatment methods and devices werediscovered during the patent search. The inventions listed below have anelement or elements similar to the invention disclosed herein; however,additional elements, details of elements, and/or applications of theinventions differ significantly from the forms and functions of thepresent invention. While the inventions listed below are intended toprovide stormwater treatment, the principle of operation for many ofthese devices is filtration rather than sedimentation.

[0027] U.S. Pat. No. 4,298,471, Dunkers, K. R., November 1981, Apparatusfor equalization of overflow water and urban runoff in receiving bodiesof water.

[0028] U.S. Pat. No. 4,377,477, Dunkers, K. R., March 1983, Apparatusfor equalization of overflow water and urban runoff in receiving bodiesof water.

[0029] U.S. Pat. No. 4,664,795, Stegall, W. A. et al., May 1987,Two-stage waste water treatment system for single family residences andthe like.

[0030] U.S. Pat. No. 4,747,962, Smissom, B., May 1988, Separation ofcomponents of a fluid mixture.

[0031] U.S. Pat. No. 4,865,751, Smissom, B., September 1989, Separationof components of a fluid mixture.

[0032] U.S. Pat. No. 5,080,137, Adams, T. R., January 1992, Vortex flowregulators for storm sewer catch basins.

[0033] U.S. Pat. No. 5,232,587, Hegemier, T. E. et al., August 1993,Stormwater inlet filters.

[0034] U.S. Pat. No. 5,322,629, Stewart, W. C., June 1994, Method andapparatus for treating stormwater.

[0035] U.S. Pat. No. 5,403,474, Emery, G. R., April 1995, Curb inletgravel sediment filter.

[0036] U.S. Pat. No. 5,437,786, Horsley, S. W. et al., August 1995,Stormwater treatment system/apparatus.

[0037] U.S. Pat. No. 5,480,254, Autry, J. L. et al., January 1996, Stormdrain box filter and method of use.

[0038] U.S. Pat. No. 5,549,817, Horsley, S. W. et al., August 1996,Stormwater treatment system/apparatus.

[0039] U.S. Pat. No. 5,702,593, Horsley, S. W. et al., December 1997,Stormwater treatment system/apparatus.

[0040] U.S. Pat. No. 5,707,527, Knutson, J. H. et al., January 1998,Apparatus and method for treating stormwater runoff.

[0041] U.S. Pat. No. 5,730,878, Rice, T., March 1998, Contaminated wastewater treatment method and device.

[0042] U.S. Pat. No. 5,744,048, Stetler, C. C., April 1998, Clogresistant storm drain filter.

[0043] U.S. Pat. No. 5,770,057, Filion, G., June 1998, Overflow waterscreening apparatus.

[0044] U.S. Pat. No. 5,779,888, Bennett, P. J., July 1998, Filteringapparatus.

[0045] U.S. Pat. No. 5,810,510, Urriola, H., September 1998, Undergrounddrainage system.

[0046] U.S. Pat. No. 5,840,180, Filion, G., November 1998, Water flowsegregating unit with endless screw.

[0047] U.S. Pat. No. 5,890,838, Moore, Jr. Et al., April 1999,Stormwater dispensing system having multiple arches.

[0048] U.S. Pat. No. 5,972,216, Acernese, P. L. et al., October 1999,Portable multi-functional modular water filtration unit.

[0049] U.S. Pat. No. 5,985,157, Leckner, J. P. et al., November 1999,Filter device.

[0050] Previous vault or box type treatment devices used in wastewateror stormwater treatment applications acted as “flow-through” systems. Inthese previous devices, incoming flows enter the device, take a givenperiod of time based on baffles and size to flow through the device, andthen exit the device. If flows were coming in continuously, they wouldenter and exit the device at the same flow rate. Previous devices havedifferent systems within the vault to channel, divert, or reduce flowrates inside the vault in order to facilitate gravity separation. All ofthese devices are somewhat effective at settling out particles down to acertain size or specific gravity, but none of these devices areeffective at removing the very small size range of particles that makeup the majority of toxic pollutants in storm water runoff. Theseparticles are typically in the 100-micron and smaller size range, andsimply will not settle out of the water if there are horizontal flowvelocities present.

[0051] Most currently available stormwater treatment devices aredesigned to reduce the concentrations of pollutants in stormwater byscreen, filter or enhanced gravitational separation (i.e. swirlconcentrators). However, such systems provide little or no detentioncapture volume to mitigate the runoff peaks for small or large runoffevents. In other words, these systems function as flow-through devices,resulting in the lack of capture volume and overall poor treatmentperformance. Specifically, much of the settleable materials trapped ordeposited during more numerous smaller runoff events are agitated andremobilized, and wash out of these devices when larger and more intenserunoff events occur.

[0052] Properly sized and maintained wet detention ponds (retentionponds) provide some of the most effective stormwater treatmentavailable. Because of site-specific limitations, however many desirablefeatures of wet detention ponds are not utilized in real worldconditions. Available surface area, possible thermal pollution,attractive nuisance liabilities, mosquitoes and long-term maintenanceaccess and disposal are some of the difficulties that must be addressedwith a surface pond.

SUMMARY OF THE INVENTION

[0053] This stormwater mitigation system solves these problems and more,and includes the benefits of a properly designed retention pond.

[0054] The apparatus advantageously settles particles down to a size of100 microns and smaller out of suspension in the stormwater by utilizinga unique volume control design. The vault of the present invention isdesigned to treat a given volume of stormwater runoff, as opposed to agiven runoff flow rate as treated in other devices. In so doing, thehorizontal flows for the entire volume of water to be treated can benearly eliminated, such that with a reduced flow rate very smallparticles may drop out of suspension and collect on the bottom of thevault. This is accomplished through a combination of physical space tocapture and hold water to be treated, restriction of flow out of theapparatus at a slower flow rate than flow into the apparatus, andvertically stacked pools of water with reduced or eliminated relativeflow velocity.

[0055] Features that are thought to provide such consistently highquality treatment advantageously include; a permanent pool (i.e., a poolessentially continuously present after it is first filled) to eliminatethe resuspension of pollutants, extended quiescent settling conditionsto promote retention of the Total Suspended Solids (“TSS”) and floatablematerials, subsurface conditions that curtail the resuspension ofdeposited sediment, sufficient volume to retain runoff from the majorityof runoff events and capture and treat the “first flush” of the largerevents, flow control system to attenuate the runoff flow rates from themajority of storm events and prevent flushing of the capturedpollutants, and large surface area that promotes oxygen transfer toreduce pollutant remobilization.

[0056] An aspect of this invention is to provide an apparatus forremoval of pollutants with densities greater than and less than waterfrom stormwater runoff.

[0057] Another aspect of this invention is to provide an apparatus thatretains and immobilizes trapped pollutants, even during periods whenflows are high.

[0058] Another aspect of this invention is to accumulate pollutants thatare less and more dense than water until a time when the apparatus iscleaned out.

[0059] Another aspect of this invention is to minimize velocity in thevicinity of the bottom of the apparatus to minimize resuspension ofdeposited sediments and associated pollutants. The slower the velocityof water in at least part of the device, the more effective will be theremoval of particles.

[0060] Another aspect of this invention is to provide an apparatus thatcan provide treatment of stormwater for larger tributary drainage areasby addition of modular sections.

[0061] Another aspect of this invention is to collect stormwater runoffand release it at a controlled rate over a specified period of time viaan outflow opening.

[0062] Other aspects and advantages will become apparent hereinafter.

[0063] In one embodiment, the apparatus includes a by-pass manhole,apparatus chambers including a plurality of interior baffles, and ajunction box. This apparatus, along with properly sized and installedancillary appurtenances, will advantageously collect and hold floatabledebris, runoff bed load particulate material, free oil and grease,settleable sediments and those dissolved pollutants including metals,nitrogen and phosphorus nutrients, and soluble organic compounds the mayadsorb or adhere to the surface of sediments and organic debris instormwater. This apparatus, properly installed and utilizing a properlysized outflow opening aperture installed within an outlet opening, cancapture and control the release of site runoff, significantly reducingerosion and stream degradation due to urbanization of the riparianhabitat, and helps restore pre-development runoff rates to urbanizedareas.

[0064] In one embodiment, the apparatus is a below grade modularconcrete stormwater control device that is designed to manage and treatstormwater runoff by diverting a predetermined capture volume (or waterquality capture volume) into the apparatus. As would be understood byone of ordinary skill in the art, the capture volume is typically sized,for example, between the mean and the maximized runoff event as definedin “Urban Runoff Quality Management,” Water Environment Federation (WEF)Manual of Practice No. 23 and American Society of Civil Engineers”(ASCE) Manual and Report on Engineering Practice No. 87. The capturevolume is surcharged into detention storage (the active pool).

[0065] This capture is brought about by a volume control diversion weirthat directs the design capture volume runoff into the apparatus with aminimum hydraulic loss into the apparatus. Any subsequent flow beyondthat of the design capture volume is allowed to bypass the apparatus viaa volume control diversion weir returning to the stormwater or runoffcollection system and/or receiving waters.

[0066] During wet weather and periods of site runoff, the detention timeof the capture volume may be optimized to promote quiescentsedimentation within the active pool whereby settable solid particlesless than 100 microns in size with a specific gravity greater than waterwill descend and insoluble oil droplets and marginally buoyant debriswill float to the surface.

[0067] One aspect of the invention is a rectangular chamber of variablelength, width and height assembled in a modular fashion. The rectangularchamber contains a system of overflow and underflow baffles, bothperpendicular to and oblique to the primary direction of flow from theinlet to the chamber to the outlet from the chamber, which are locatedat opposite ends of the rectangular chamber. The baffles in the chamberserve several purposes including: flow momentum and energy dissipation,creation of a tortuous flow path, retention and immobilization ofpollutants less and more dense than water, minimization of resuspensionof sediments, and minimization of remobilization of floatable pollutantsinto the water column. The primary process for pollutant removal isgravitational separation, which occurs while water is detained in thechamber.

[0068] A baffle configuration for minimization of resuspension oftrapped sediments and associated pollutants was first conceptualized bythe inventors and then optimized by iterative experimentation involvingthree dimensional velocity measurements and dye visualization for aplurality of baffle configurations using a geometrically andhydraulically scaled physical model. Baffle configurations wereevaluated for both dynamic (chamber filling and draining) andsteady-state (chamber full with inflow rate equal to outflow rate)conditions. This exhaustive experimentation indicates that the baffleconfiguration of the invention disclosed minimizes resuspension of fineand coarse sediments and associated pollutants to a degree that exceedsthe capabilities of prior art. In addition, a trapezoidal underflowbaffle, the shape of which was optimized during hydraulicexperimentation, impedes material less dense than water from enteringthe outflow section and exiting the vault. The trapezoidal configurationhas the advantage of decreasing the downward velocity of waterapproaching and then moving under the baffle and into the outlet sectionand, thereby, decreases the risk of entraining floatable pollutantstrapped behind the trapezoidal baffle into the flow passing into theoutlet section. As a result, the plurality of interior baffles and theweir configuration advantageously are designed to provide minimumre-suspension of settable solids from within the permanent pool.

[0069] In one aspect, the apparatus has an inlet that delivers water tothe chamber from a tributary surface land area, either directly or viastorm sewer system piping. Water entering the chamber passes through asystem of underflow and overflow baffles both perpendicular to andoblique to the primary direction of flow from the inlet to the outlet,which is located at the end of the rectangular chamber opposite theinflow. As water enters the chamber, the water level in the chamberrises above the permanent pool water surface elevation, which normallyis less than or equal to the elevation of the invert of the outflowopening. Outflow from the chamber is controlled by an opening that issized to provide a specified time for the water in the chamber to drainfrom the elevation at which the chamber is full to the elevation of thepermanent pool. When the rate of inflow is greater than the rate ofoutflow, the water level in the chamber will rise to the elevation atwhich the chamber is full. Once the chamber is full, any flow in excessof the outflow rate under full conditions will bypass the chamber via anoverflow structure 294. When the rate of outflow is greater than therate of inflow, the water surface elevation in the chamber will decreaseat a rate controlled by the size of the outflow opening, and the watersurface elevation will decrease to the elevation of the outflow openinginvert, at which time outflow will cease. For convenience and brevity,this chamber inflow volume, as described in previous applications, isherein called a capture volume.

[0070] By slowly metering out storm runoff back to the externalenvironment, the apparatus is of great benefit as it not only removespollutants but also duplicates runoff conditions that exist prior tourban development. This prevents erosion of stream channels, and alsoprevents a discharge of rapidly flowing runoff that would simply pick upmore sediment after treatment.

[0071] Another aspect of the invention is a stormwater treatmentapparatus, including a receptacle adapted to receive water flowing froma surface drainage area, the receptacle having a bottom and a top, thereceptacle having an inlet and an outlet, the inlet and the outlet beingin fluid communication with one another; and at least one bafflepositioned within the receptacle between the inlet and the outlet, thebaffle extending from the bottom of the receptacle, a first portion ofthe baffle and the bottom of the receptacle forming an angletherebetween.

[0072] A stormwater treatment apparatus varies from other types oftreatment apparatus, such as septic tanks, in that stormwater treatmentapparatus must capture a wide variety of particles of different sizesand compositions in a pulsed hydraulics environment, as opposed to themore constant flow environment of a septic tank. A stormwater treatmentapparatus also differs from septic tanks in that the goal is topermanently trap sediments and other pollutants less or more dense thanwater, rather than to degrade organic matter and other biodegradablesubstances and in that a stormwater treatment apparatus is much largerthan septic tanks, desirably having a volume of at least 500 cubic feet,more desirably at least 600 cubic feet and, preferably, at least 750cubic feet. Generally, this apparatus size advantageously is sized toinclude an active pool volume sufficient to treat the capture volume ofthe area being treated. Additionally, one vault or more than one vaultmaybe used, depending on the topography of the area being treated, andsize of the vault(s) being used. Factors effecting the size and numberof vaults used in the apparatus, besides capture volume, includemanufacturing capability, transportability to site, modularity ofapparatus, cost of construction and installation, site topography, easeof installation, and apparatus footprint.

[0073] The apparatus advantageously substantially reduces bottomvelocities, thereby greatly reducing resuspension of sediments. Inparticular, the angle formed between the first portion of the baffle andthe bottom of the receptacle is desirably between 30 and 60 degrees, atis desirably inclined in a downstream direction. Further, the height ofthe baffle is desirably at least two feet to limit the washing out ofsediment. To facilitate manufacture and cleaning the baffle desirablyincludes a second portion, the second portion of the baffle extendingfrom the bottom of the receptacle and forming an angle with the bottomof the receptacle, the angle being roughly 90 degrees.

[0074] The apparatus desirably includes an inlet baffle positionedbetween the inlet and the outlet, the inlet baffle spaced from saidbottom and extending between generally opposing walls and an outletbaffle positioned between the inlet and the outlet, the outlet bafflespaced from said bottom and extending between generally opposing wallsof the receptacle. The lower end of the outlet baffle is desirablypositioned below said outlet. The outlet baffle advantageously maydefine a horizontal cross-section between a first baffle extending fromsaid bottom and said outlet baffle larger than the horizontalcross-section between said first baffle and a vertical plane tangent toan upstream side of said outlet baffle. This has the effect of reducingthe velocity of fluid. In this regard, it is desirable that outletbaffle defines a center section and at least one outer section whichextends toward said outlet from said center section. Advantageously,however, the spaces between the outlet baffle and the opposing walls aresufficiently large to permit cleaning and to facilitate manufacture.

[0075] Yet another aspect of the invention is an apparatus for cleaningstormwater runoff, the apparatus including a vault having a top, abottom, two sides, a front and a back, the vault comprising a firstbaffle extending from the bottom of the vault; a second baffle extendingfrom the bottom of the vault, an inlet section having an opening and anoutlet section having an outlet opening.

[0076] The apparatus also advantageously includes vertically stackedcolumns of water, defined by, in one embodiment, varying horizontal flowrates and bounded by baffles creating regions of lower horizontal flowrate. When the vault is filling or full, there is a column of water,called for convenience an “active pool,” that is filling via the inlet,draining via the outlet, or both. This pool is the water being held,treated, and released by the invention. As the active pool is treated,sediments settle to the floor of the vault. As a result, when there iswater in the active pool, it has a significantly higher velocity thanthe water in the permanent pool. A typical flow velocity for the activepool is two to three feet per second.

[0077] In order to retain sediments and to prevent them from running outof the vault as it empties, and in order to prevent resuspension of thesediments as the vault refills at a later time, the apparatusadvantageously includes a permanent pool. The permanent pool sitsimmediately below the active pool and receives most or all sediments asthey drop out of the active pool. Due to the shape, design and spacingof the baffles surrounding and within the permanent pool and activepool, the permanent pool is an inactive pool (a permanent pool that hasminimal to no flow velocity.) Based on tests, the inactive permanentpool of the preferred embodiment of this invention maintains flowvelocities typically below 0.15 feet per second.

[0078] One of the failings of prior “flow-through” systems was theirinability to settle small particles from smaller storm flows withoutresuspending those particles in later large storm flows due toturbulence and currents that reach all areas of the prior vaults. Thepresent apparatus, by creating an active pool that fills, holds anddrains immediately above an inactive permanent pool, eliminates smallparticle re-suspension. Even in prior systems, simply applying bafflesto create a physical barrier to sediments moving horizontally throughthe system, without creating a permanent pool, is only effective forlarger, heavier particles: in prior flow-through systems, smaller andfiner particles, which form the majority of toxic pollutants, are leftwithout an inactive permanent pool area to reside in and are simplysuspended (or re-suspended) in the flow as it moves from compartment tocompartment and exits.

[0079] A further advantage of vertically stacked pools including apermanent pool is that of maintaining a compact footprint or plan area.By both treating the incoming volume of water and storing sediments inthe same plan area more water volume can be treated on a given site.

[0080] Finally, the present invention advantageously includes anoverflow structure, in one embodiment integral to the outlet section ofthe vault. When inflow of stormwater exceeds the volume capacity of thetreatment system, the overflow structure diverts excess stormwater flowwithout substantially effecting the ability of the system to effectivelytreat the full volume of stormwater already in the vault.

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] One embodiment of this invention, the best mode, is illustratedin the attached drawings, in which like numerals indicate likecomponents throughout the several views. Views include:

[0082]FIG. 1—a plan (from a perspective above the apparatus) view of theapparatus that is the subject of this invention;

[0083]FIG. 2—a profile (side elevation) view of the apparatus;

[0084]FIG. 3—a cross-sectional view of the inlet section of theapparatus (cross-section 1-1 shown on FIG. 1 and FIG. 2);

[0085]FIG. 4—a cross-sectional view of the outlet section of theapparatus (cross-section 2-2 shown on FIG. 1 and FIG. 2);

[0086]FIG. 5—a detailed (enlarged) profile view of the inlet sectionbaffle configuration;

[0087]FIG. 6—a detailed plan view of the outlet section

[0088]FIG. 7—a detailed view of the outflow opening configuration;

[0089]FIG. 8—an illustration of baffle spacing for this invention foreven and odd numbers of chambers for a multi-chambered apparatus (thenumber of midsections depicted in this view, four for the evenillustration and five for the odd illustration, are specific examples ofthe generalized odd and even baffle spacing rules and are not intendedto be restrictive);

[0090]FIG. 9—an illustration of a modified embodiment of the presentinvention, including an external bypass structure;

[0091]FIG. 10—an illustration of the apparatus, in one embodiment,incorporating a gravity dynamic flow control orifice; and,

[0092]FIG. 11—a detail plan view of the apparatus, in one embodiment,incorporating an integral overflow bypass structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0093] The drawings illustrate one embodiment of an apparatus 100 forseparation of pollutants that are less and more dense than water fromstormwater runoff. Referring to FIG. 1 and FIG. 2, the apparatus 100consists of a top 140, a bottom 160, an inlet end 170, an outlet end150, a left side 300, and a right side 310 (left and right are relativeto the view from the inlet end 170 to the outlet end 150). These sidesdefine a rectangular chamber with an inlet section 110, an outletsection 120, and one or more midsections 130.

[0094] The length of the most basic configuration of the apparatus 100is desirably at most 20 ft, more desirably at most 18 ft 6 in, and, mostpreferably, 17 ft 6 in (inside dimension); and the width of theapparatus id desirably at most 10 ft, more desirably at most 8 ft 6 in,and, most preferably, 7 ft 6 in (inside dimension); the height of theapparatus is 6 ft or 8 ft (inside dimensions). Outside dimensions andinside dimensions may vary due to structural strength requirements ofthe apparatus 100. Desirably, the length of the apparatus 100 increasesin 4-ft, 8-ft, or 16-ft increments as additional midsections 130 areemployed. The top 140 and bottom 160 are desirably parallel to eachother and are separated by a distance of 6-ft or 8-ft (insidedimensions). The left side 300 and right side 310 are desirably parallelto each other and are separated by a distance of at most 10-ft, moredesirably 8-ft 6-in and, preferably, 7-ft 6-in (inside dimensions). Theinlet end 170 and the outlet end 150 are desirably parallel to eachother and, for the most basic configuration, are desirably separated bya distance of at most 20-ft and, more desirably, 17-ft 6-in (innerdimension). The distance between the inlet end 170 and the outlet end150 desirably increases by 4-ft, 8-ft, or 16-ft increments as additionalmidsections 130 are employed. The thickness of the inlet end wall 170,the outlet end wall 150, the left side 300, the right side 310, and thebottom 160 is desirably at least 3-in and, preferably, 6-in or more. Thethickness of these walls may increase or decrease as structural needs ofan installation dictate. The thickness of the top 140 of the apparatus100 is at least 3-in and, desirably, 6-in or more but may increase ordecrease as structural needs of an installation dictate.

[0095] Based on experience gained after the filing of the originalapplication, it is currently believed that the preferred dimensions forthe apparatus are a length of about eighteen feet (along the longestdimension of the apparatus), a width of about eight feet, and a depth ofabout eight feet. As the apparatus is made larger, though, itadvantageously can treat a larger capture volume of stormwater. Thepreferred method of increasing the size of the apparatus is to addmodular midsections to increase the length and treatment capacity of theapparatus. Desirably, the apparatus can thus range from a basicconfiguration of about eighteen feet in length to compound, largeconfigurations of approximately one hundred feet in length including aplurality of midsections. As topographical, footprint, transportation,manufacturing and capture volume requirements change, these structuraldimensions may similarly change.

[0096] The ability to increase the size and treatment capacity of theapparatus 100 by addition of modular midsections 130 is advantageous formanufacturing since the apparatus 100 can be manufactured in a widerange of incremental sizes using the same set of forms for precasting.In addition, the modular construction is favorable for applicationsrequiring a large apparatus 100 as the modular sections 110, 120, and130 can be transported on one or more trucks and then assembled on-site.The incremental sizing may be advantageous for performance at improvingwater quality as well when the apparatus 100 is sized according tomanufacturer's recommendation. For example, if a user, based on sizingcalculations, determines that the required capacity of the apparatus 100necessary to achieve a desired performance is equivalent to the capacityof a midsection with a length of 11-ft, then the user would specify that2 midsections 130 are needed, one 8-ft long and the other 4-ft long (ortwo 8-ft long sections), since midsections 130 are discrete componentsand 1 mid-section 130 would not provide the required capacity. As aresult of this modular, incremental sizing, the apparatus 100 specifiedby the user would always have a capacity equal to or in excess of thatrequired and would, therefore, provide a minimum degree of desiredtreatment.

[0097] A plurality of baffles 220 and 250 are positioned between theinlet end 170 and the outlet end 150. The primary direction of flow isdefined as the direction from the inlet end 170 toward the outlet end150 in the horizontal plane. In the disclosed embodiment, the primarydirection of flow is perpendicular to the inlet end 170 and the outletend 150 and parallel to the top 140, bottom 160, left 300, and right 310sides. There are two types of overflow baffles employed in thisinvention. These baffles are referenced as components 220 and 250.Component 220 is a hybrid baffle, and component 250 is an angled baffle.The results of extensive hydraulic testing indicate that the baffleconfiguration illustrated, as well as the claimed baffle configurationsusing various combinations of hybrid 220, vertical, and angled 250baffles, is highly effective at minimizing resuspension of trappedsediments and associated pollutants. Velocity measurements and dyevisualization experiments indicate that the apparatus 100 disclosedherein provides a degree of reduction of resuspension that significantlysurpasses that of existing art.

[0098] Referring to FIG. 1, FIG. 2, and FIG. 5, the hybrid baffle 220consists of a vertical section 240 that is perpendicular to the primaryflow direction and an angled section 230 that is oblique to the primarydirection of flow, forming an angle, α, with the horizontal plane (angleα is depicted in FIG. 5). Preferably, the vertical baffle section 240has a length of 1-ft and the angled section of the baffle 230 rises fromthe top of the vertical section 240 at a 45° angle for a distance of1-ft in the horizontal plane and a distance of 1-ft in the verticalplane. Preferably, the total vertical rise for a hybrid baffle 220 is2-ft from the chamber bottom 160, and the horizontal projection is 1-ft3-in. in the downstream direction (including thickness of the verticalsection 240). An angle other than 45° may be used for the hybrid baffle220 as long as the lengths of components 230 and 240 are adjusted toprovide a total rise of 2-ft and the downstream end of component 230does not extend beyond the dimensions of the top 140, bottom 160, andwalls 300, 310, and 170 of the precast unit containing the baffle.Desirably, the angle α is between 0° and 90°, and, more desirably,between 30° and 60° degrees.

[0099] The angled baffle 250 rises 2-ft from the bottom of the chamber160. An angled baffle 250 is illustrated in FIG. 1 and FIG. 2 in planand profile views, respectively. For the best mode, the baffle 250 formsan angle, α, of 45° with the chamber bottom 160. An angle other than 45°may be used, provided that a vertical rise of 2-ft is maintained andthat the downstream end of the angled baffle 250 does not project beyondthe end of the associated 8-ft midsection 130. Hybrid baffles 220 andangled baffles 250 may be interchanged to create numerous embodiments;however, the best mode utilizes a single hybrid baffle 220 in the inletsection 110 and angled baffles 250 in midsections 130, the spacing ofwhich is described below. Other shapes and heights of baffles, up to thefull depth of the permanent pool have been tested and are viablealternates to the “best design” shown herein and are part of the designclaims of this apparatus 100.

[0100] Extensive hydraulic experimentation and testing of baffleconfigurations and types was conducted to determine baffle geometry thateffectively reduced velocities in the lower section of the apparatus 100where sediments accumulate after settling out of the water. As will beappreciated by one of skill in the art, the creation of this reducedvelocity region results in a region of little or no velocity near thegravitational bottom of the vault. That is, this region comprises aninactive permanent pool. Initial testing indicated that angled baffles250 were more effective than vertical baffles at decreasing bottomvelocities in the apparatus' midsections 130. The inventors initiallytested angled baffles 250 for the purpose of examining the effect of theangled baffles 250 on flow passing over the crest of the angled baffles250. In the process of this experimentation, the inventors discoveredthat the angled baffles 250 had a favorable effect on bottom velocitiesbetween two angled baffles 250 separated by a distance of 16-ft or less.A hybrid baffle 220 was developed and tested for the purpose ofachieving a reduction in bottom velocities in the midsections 130comparable to that found using an angled baffle 250, while at the sametime decreasing the length in the horizontal plane consumed by theangled baffle 250 by a distance equivalent to the product of the heightof the vertical portion of the baffle 240 and the tangent of the angle90°−α. This reduction in the horizontal distance required to accommodatethe hybrid baffle 220 allows the inlet section 110 to be shortened,resulting in a reduction in the amount of material necessary tofabricate the inlet section 110. In addition, the vertical portion 240of the hybrid baffle 220 has the advantage of improved access for a hoseor vacuum to clean out the area beneath the baffle 220. An angled baffle250 permits access beneath the baffle 250 for cleaning only where thedistance between the under-surface of the baffle 250 and the bottom ofthe chamber 160 (inside dimension) is greater than the diameter orheight of the intake component of the vacuum or pumping cleaning system.For both angled 250 and hybrid 220 baffles, the experimentationconducted indicated that both types of baffles 250 and 220, performedvery well at evenly distributing flow across the width of the apparatus100.

[0101] Water is supplied to the apparatus inlet section 110 via an inletpipe or other conveyance 180 carrying water from the tributary drainagearea to the inlet of the apparatus 190. The invert of the inlet aperture190 is desirably at least 3-ft above the chamber bottom 160 (insidedimension). The apparatus 100 may also receive water from the tributarydrainage area directly rather than via an up-gradient, piped storm sewersystem. An example of this configuration would be an apparatus 100installed to receive water from a manhole chamber below a curb-side dropinlet.

[0102] The inlet section 110 consists of several distinct componentsthat are shown in FIG. 1, FIG. 2 in plan and profile views,respectively. FIG. 3 shows a cross-section (1-1) of the inlet section110, and FIG. 5 shows details of the baffle configuration for the inletsection 110. The dimensions of the inlet section 110 are defined by theinlet end wall 170; the top 140, bottom 160, left 300, and right 310sides; and a plane perpendicular to the primary direction of flowlocated a prescribed distance from the inside dimension of the inlet endwall 170 in the downstream direction. This prescribed distance isdefined by the length dimension of the precast segment containing theenergy dissipation baffle 200 and the most upstream hybrid 220 or angled250 baffle and, most preferably is 4-ft 9-in. The dimensions of theinlet section 110, exclusive of baffles, desirably are equivalent to thedimensions of the outlet section 120, providing the advantage of havingthe capability to cast inlet 110 and outlet 120 sections using the sameform. The inlet section 110 desirably includes a manhole 135 for accessto the inlet section 110 for maintenance. The cover of the manhole 135is desirably vented to allow exchange of air between the inside of theapparatus 100 and the surface atmosphere to prevent anoxic conditionsfrom developing in the permanent pool. The permanent pool is defined asthe volume of water and trapped pollutants in the apparatus 100 abovethe bottom of the chamber 160 and below the invert of the outflowopening 280.

[0103] A component of the inlet section 110 is a flow energy dissipationbaffle 200 that is perpendicular to the primary direction of flow. Theenergy dissipation baffle 200 is parallel to the inlet end wall 170 andis positioned so that the side of the energy dissipation baffle 200facing the inlet wall 170 is desirably at most 1-ft 6-in and preferably1-ft from the inner side of the inlet end wall 170 in the primarydirection of flow. The energy dissipation baffle 200 desirably isconnected to the left side 300 and right side 310 from a distance ofdesirably at most 2-ft and preferably 1-ft 6-in above the chamber bottom160 (inside dimension) to a distance of desirably at most 1-ft, andpreferably 6-in from the chamber top 140 (inside dimension). The energydissipation baffle 200 desirably has a thickness of 3-in. The purpose ofthe flow energy dissipation baffle 200 is to decrease the energy of theincoming flow. For the apparatus 100 described herein, the decrease inflow energy translates to a decrease in the velocity of the incomingwater. The space 210 is provided between the top of the energydissipation baffle 200 and the top 140 of the apparatus 100 for thepurpose of allowing overflow for high flows and for the purpose ofproviding access for maintenance. Hydraulic testing indicates that theenergy dissipation baffle 200 is effective at decreasing flow energy.The inventors examined several options for spacing between the inlet endwall 170 and the flow energy dissipation baffle 200 and found that theabove-described spacing provided a good balance between theeffectiveness of energy dissipation and the space necessary to accessthe area between the inlet end wall 170 and the baffle 200 formaintenance.

[0104] Another element of the inlet section is the inlet overflow baffle220. The inlet overflow baffle 220 is a hybrid baffle (described above).The inlet overflow baffle 220 desirably is connected to the chamberbottom 160 and the left 300 and right 310 sides of the chamber so thatwater can only pass over the top of the baffle, defined by component230. The vertical portion 240 of the inlet overflow baffle 220 desirablyis located a distance of at least 2-ft 6-in, more desirably at least3-ft, and preferably 3-ft 6-in from the inlet end wall 170 (insidedimensions). The thickness of the inlet overflow baffle 220 is desirably3-in. The vertical rise for the inlet overflow baffle 220 is desirablyat most 3-ft, more desirably at most 2-ft 6-in, and, preferably, 2-ft,and the horizontal distance in the direction of flow is desirably atmost 2-ft, more desirably at most 1-ft 6-in, and, preferably, 1-ft 3-in(including the baffle thickness of 3-in) for the best mode.

[0105] A midsection 130 of the apparatus 100 is defined by a top 140, abottom 160, a left 300, and a right 310 side that desirably areconnected at 90° angles to form an open-ended rectangular section. FIG.1 and FIG. 2 depict an apparatus 100 with two, 8-ft midsections 130. Theapparatus 100 desirably has at least one midsection 130 but may haveadditional midsections 130. Desirably, the midsections 130 have a lengthof 16-ft, more desirably 4-ft, and, preferably, 8 ft. Angled baffles 250desirably are spaced at 4-ft increments, more desirably at 8-ftincrements, and, preferably, at 16-ft increments in midsections 130. Formidsections 130 requiring angled baffles 250 to achieve this spacing, anangled baffle 250 (described above) is attached to the bottom of themidsection 130 so that the downstream tip of the angled baffle 250coincides with the end of the midsection 130. Such an angled baffle 250in a midsection 130 is shown in FIG. 1 and FIG. 2 in plan and profileviews, respectively. While an angled baffle 250 desirably is used in themidsections 130, vertical, hybrid, or other baffle shapes 220 may beused. Since baffle 220 and 250 spacing is preferably 16-ft andmidsections 130 are added in 4-ft, 16-ft, or 8-ft increments, not allmidsection segments 130 will need baffles 220 and 250. FIG. 8illustrates baffle 220 and 250 spacing. As FIG. 8 indicates, baffles 220and 250 preferably are spaced every 16-feet, and a baffle 220 and 250 isdesirable at the end of the most downstream midsection 130. Therefore,for an even number of midsections 130, desirably with a length of 8-ft(four as an example in FIG. 8), all overflow baffles 220 and 250 arepreferably spaced 16-feet apart. For an odd number of midsections 130,desirably with a length of 8-ft, (five as an example in FIG. 8),however, spacing is preferably 16-feet between all overflow baffles 220and 250 with the exception of the spacing between the penultimate andultimate downstream baffles 220 and 250 at the end of the mostdownstream midsection 130. The number of midsections 130 depicted inFIG. 8 are shown as examples of even and odd numbers of midsections 130and should not be interpreted as restrictive specifications. Eachmidsection 130 desirably will have a manhole 135, allowing accessthrough the top of the chamber 140 for maintenance. Desirably, allmanholes 135 will be vented to prevent development of anoxic conditionsin the permanent pool and will be of sufficient size to allow thecontents of the apparatus 100 to be pumped out as a part of regularmaintenance. Manholes 135 positioned above midsections of the apparatus100 desirably will have a collar 145 with approximately the same innerdiameter as the manhole that extends into the chamber 3-in below the top140. The purpose of the collar 145 is to limit the surface area of thewater and associated floatable pollutants in the chamber that couldpotentially be forced out of the apparatus 100 via vents in manholeaccess areas 135 when the apparatus 100 fills completely.

[0106] The midsection 130 components of the apparatus 100 are theprimary treatment and pollutant collection chambers. During the timethat water is detained in the apparatus 100, sedimentation occurs,resulting in deposition of sediments and associated pollutants withdensities greater than water on the bottom 160 of the midsections 130.The configuration of baffling 220 and 250 is such that sedimentsdeposited on the bottom 160 of the midsections 130 resist resuspensionduring subsequent runoff events. Once the thickness of the sedimentlayer on the bottom 160 of the midsections 130 increases to a prescribeddepth, the apparatus 100 is cleaned via a pump-out or other method toremove the permanent pool and trapped pollutants from the apparatus 100for disposal.

[0107] In addition to sediment removal, the midsections 130 of theapparatus 100 collect and retain materials less dense than water. Duringthe time that water is detained in the apparatus 100, materials that areless dense than water rise toward the water surface. Since flow from themidsections 130 passes to the outlet section 120 by flowing beneath thetrapezoidal baffle 260, pollutants on the water surface in themidsections 130 are retained on the upstream side of the trapezoidalbaffle 260. Due to the elevation of the invert of the outlet opening280, the surface of the permanent pool in the apparatus 100 desirablyremains at least 1-ft above, and, preferably, 1-ft 5-in above thehighest elevation at which water can pass below the trapezoidalunderflow baffle 260. As described below, the trapezoidal geometry ofthe underflow baffle 260 is advantageous for prevention of entrainmentof pollutants collected on the surface of the mid-sections 130 into theflow beneath the trapezoidal baffle 260 entering the outlet section 120.Desirably, a mat or mats composed of material capable of absorbingpetroleum-based hydrocarbons with densities less than that of water willbe placed in the midsections 130 of the apparatus 100 for the purpose ofimmobilizing these pollutants. Manholes 135 will be large enough topermit removal of the absorbent mats.

[0108] A detailed plan view of the outlet section 120 is shown in FIG.6, and a detail of the outflow opening configuration 280 is shown inFIG. 7. The dimensions of the outlet section 120 are defined by theoutlet end wall 150; the top 140, bottom 160, left 300, and right 310sides; and a plane perpendicular to the primary direction of flowlocated 4 ft 9 in from the inside dimension of the outlet end wall 150in the upstream direction. The dimensions of the outlet section 120,exclusive of baffles, are equivalent to the dimensions of the inletsection 110, providing the advantage of having the capability to castinlet 110 and outlet 120 sections using the same form.

[0109] One component of the outlet section 120, is a trapezoidalunderflow baffle 260. In the plan view (FIG. 1 and FIG. 6), thetrapezoidal underflow baffle 260 desirably consists of a center segmentparallel to the outlet end wall 150 and a pair of outer segments. Thecenter segment is located desirably at least 2-ft, more desirably 3-ft,and, preferably 4-ft from the outlet end wall 150 (inside dimension ofend wall to upstream side of trapezoidal baffle 260). The center segmentof the baffle 260 is centered with respect to the left 300 and right 310sides of the chamber. Preferably, the length of the center segment 260is 1-ft and, as a result, the distance between the ends of the centersegment of the baffle 260 and each wall 300 and 310 is 3-ft 3-in. In theplan view, the trapezoidal baffle extends from the ends of the centersegment to the corners defined by the intersection of the left side wall300 and the outlet end wall 150 and the right side wall 310 and theoutlet end wall 150. In the profile view (FIG. 2), the trapezoidalbaffle 260 is located so that the bottom of the baffle 260 desirably isat most 1-ft 11-in and, preferably, 1-ft 6-in above the bottom of thechamber 160 (inside dimension). The baffle 260 extends to the top of thechamber 140 and is joined to the top of the chamber 140 along thetrapezoidal-shaped top edge of the baffle 260 displayed in the plan view(FIG. 1 and FIG. 6). The trapezoidal underflow baffle 260 desirably isalso attached to the sides of the apparatus 100 where the left and rightsides 300 and 310, respectively, form corners with the outlet end 150from a distance, preferably, 1-ft 6-in above the bottom of the chamber160 (inside dimension) to the top of the chamber 140.

[0110] Initially, the inventors tested a simple, vertical underflowbaffle with a thickness of 3-in that was positioned in a plane entirelyperpendicular to the outlet end wall 150. This incarnation of theunderflow baffle was located a distance of 4-ft from the outlet end wall150 (inside dimension of end wall to upstream side of underflow baffle)and resulted in an area of 5.625 ft² between the downstream end of theangled baffle 250 and the upstream side of the underflow baffle in theplan view (see FIG. 1). The inventors investigated the trapezoidalunderflow baffle 260 of the present invention for the purpose ofdecreasing the velocity of the flow passing through the plane betweenthe downstream end of the angled baffle 250 and the upstream side of theunderflow baffle 260 in the plan view. The area in the plan view betweenthe downstream end of the angled baffle 250 and the upstream side of theunderflow baffle 260 is preferably 18.625 ft². Comparison of the areasbetween the underflow baffle and the upstream angled baffle 250 for thevertical underflow baffle configuration and the trapezoidal underflowbaffle 260 configuration indicates that for equivalent rates of flowpassing between the upstream angled baffle 250 and the underflow baffle,the velocity for the vertical baffle configuration preferably would be3.3 times greater than the velocity for the trapezoidal baffle 260configuration. The lower velocity attained using the trapezoidal baffle260 configuration of the present invention is advantageous forprotection from entrainment of pollutants residing on the surface layerof the midsections 130 into the flow from the midsection 130 to theoutlet section 120. Desirably, the angle between the center segment ofthe baffle and the outer segments of the baffle is between 90° and 180,more desirably between 120° and 160°, and, preferably 130°.

[0111] Another component of the outlet section 120 is outlet screening270 which is designed to keep trash and/or debris from clogging theoutlet opening 280. The outlet screening 270 consists of fine screeningor a fine mesh configured as a semi-circle, arch, rectangle, or straightscreen in front of the outflow opening 280. The screening is attached tothe outlet end wall 150 a horizontal distance in front of the outletopening that is proportionate to the outlet opening size, but no lessthan 2 times the diameter of the outlet opening and to the bottom 160and top 140 of the chamber so that all water passing through the outflowopening 280 will have first passed through the screening 270. Thescreening 270 will be attached in a manner that will permit removal andcleaning of the screening via an access manhole 135 located in the topof the outlet section 120. The cover for the manhole 135 will be ventedto allow exchange of air between the inside of the apparatus 100 and thesurface atmosphere to abate development of anoxic conditions in thepermanent pool and to relieve air pressure as the apparatus fills anddrains with water.

[0112] The outflow opening 280, shown in FIG. 1, FIG. 2, and FIG. 4 isthe device controlling the release of water from the apparatus 100. Adetail of the outflow opening 280 components is shown in FIG. 7. Theoutlet desirably consists of an 8-in diameter pipe 290, desirablyextending from 3-in upstream of the outlet end wall 150 (insidedimension), through the outlet end wall 150. The end of the pipe 290that is inside the apparatus 100 desirably is covered with an 8-in cap282. An opening 280 that is sized to provide a predetermined time forthe water in the chamber to drain from the elevation at which theapparatus 100 is full to the elevation of the permanent pool is machinedinto the 8-in cap 282. The opening 280 is manufactured so that thelowest point of the opening is preferably at least ½-in above the lowestpoint of the 8-in pipe 290 at the end where the cap 282 is attached.

[0113] An advantage of creating the outflow opening aperture 280 in acap 282 that is placed over the end of the outflow pipe 290 that isinside the outlet chamber is that the opening size can be changed asdesired during maintenance by replacing the cap 282 with another cap 282with a different sized opening 280. This flexibility in opening 280sizing is advantageous for providing an apparatus 100 that can providean array of treatment levels. The opening aperture size 284 dictates thetime that water is detained in the apparatus 100. A smaller openingaperture size 284 would result in detention of water for a longer periodof time than that afforded by a larger opening size. The treatmentefficiency of an apparatus 100 will increase as the time that water isdetained increases. Therefore, the level of treatment can be adjusted byincreasing the opening size (decreasing the level of treatment) ordecreasing the opening size (increasing the level of treatment). Anotheradvantage of the outflow opening configuration 280, is that thepositioning of the opening invert, preferably, a distance of 2-ft 11-inabove the bottom 160 and downstream of all baffling 200, 220, 250, and260 results in release of water with the lowest sediment concentrationsthrough the opening 280. An outflow opening 280 positioned lower thanthat in the illustrated embodiment would draw more water from the lowerpart of the outlet section 120, which would contain more suspendedsediments. An outflow opening 280 positioned higher than that in theillustrated embodiment would result in a greater permanent pool volumethat would need to be pumped out during maintenance.

[0114] The apparatus, being an off line type below grade structuralstormwater control device, in one embodiment manages the recommendedcapture volume—sized for a mean runoff event following the sizingcriteria as outlined in, for example, the “Urban Runoff QualityManagement”, WEF Manual of Practice No. 23, and ASCE Manual and Reporton Engineering Practice No. 87 or other source known to one of ordinaryskill in the art.

[0115] Storm events are, in one embodiment, handled by diverting thatpercentage of stormwater events from the site storm drainage collectionsystem. The apparatus advantageously provides adequate time for thecapture volume within the active pool for pollutants with specificgravities of lesser or greater than water to be captured within thehydraulically designed plurality of baffling within the permanent pool(i.e., permanent pool), reducing sediment resuspension, retainingfloating debris and hydrocarbons, and trapping neutrally buoyant trash.

[0116] As known to one of ordinary skill in the art, a mean runoff eventis typically defined, for example, as the event resulting from the “meanstorm precipitation depth, which is the depth of all runoff-producingstorms (total precipitation of 2.5 mm or 0.10″ or more) from a long-termprecipitation record for a given location, using a six-hour separationto define each storm event. This “mean storm event capture volume” willtypically result in the capture of roughly 70% of all runoff-producingevents in their entirety or approximately a “two-year storm,” defined asa stormwater event that occurs on average once every two years, orstatistically has a 50% chance on average of occurring in a given year.Other methods for determining the capture volume can similarly beemployed, depending on site requirements.

[0117]FIG. 9 illustrates one embodiment of the present invention,including an external bypass structure. In this embodiment, theapparatus 100 inflow rate is controlled by a site-specific designedcontrol weir 410 housed within a bypass manhole 400 of the typewell-known to those of ordinary skill in the art. Influent enters thesystem from a drainage system, as well known to one of skill in the art,from a sewer system main or, for example, an inflow pipe 184. Theproperly sized weir 410 diverts the site runoff into the apparatus 100through the apparatus influent pipe 180. Bypass pipes 430 divert excesswater volume beyond the maximum capture volume by diverting excess watervolume over the control weir 410 and through the bypass pipes 430. Thebypass manhole 400 is typically accessed by an access manhole 135.

[0118] The energy dissipation baffle 200 is so located to diffuse andcreate a laminar flow of the turbulent high velocity stormwater runoffon entry into the apparatus 100. The baffle is angled to extend towardthe front of the vault as it extends downward. The reduced energystormwater is diverted in less turbulent lower velocity downward againstthe bottom of the apparatus 100, and under the energy dissipation baffle200 to be directed upward by the hybrid baffles 220. The capture areabetween the energy dissipation baffle 200 and the inlet end wallprovides an area for the capture and retention of the larger and morebuoyant trash and debris, as known in the art, in a forebay trashcompartment 440. This trash area is accessed via a manhole 135 forsubsequent collection and removal of sequestered debris via vacuumsuction lift or other mechanical means. Advantageously, the forwardangled energy dissipation baffle 200 permits easy access via the manhole135 while providing additional energy dissipation.

[0119] The hybrid-baffles 220 (including, for example, 230, 240 and 250)are so located with respect to the energy dissipation baffle 200 todirect the initial and subsequent stormwater inflow in an upwarddirection thereby providing a laminar flow pattern in the active pool450 reducing the turbulence in the inactive permanent pool 460 to nearzero, thus preventing resuspension of previously settable materials. Theavailable active pool 450 above the permanent pool 460 provides avertically stacked water column desirably sized to accommodate thedesign capture volume.

[0120] This ability to exploit the vertically stacked water columnconfiguration provided by the preferably rectangular design of theapparatus 100 enhances the ability to capture stormwater runoff from asite. By simply selecting the appropriate water volume, the apparatus100 can significantly reduce erosion and stream degradation fromincreased flows due to urbanization and help restore pre-developmentrunoff rates. Due to an effective stacked water column volume control,the apparatus has superior pollution removal and retention capabilitiesthe apparatus advantageously mitigates downstream erosion and riparianhabitat degradation through retaining and slowly metering out thecapture volume, through the properly sized outflow opening aperture 284installed within outlet opening 280, flow from each event.

[0121] Intermediate angled baffle(s) 220 are so arranged to provideoptimum volume and sediment control spacing by maintaining the upwarddirectional stability of the stormwater inflow. These sediment controlbaffles 220 advantageously provide an uninterrupted quiescent area ofcapture volume to sequester settable solids and pollutants, reducing theprobability of resuspension during the introduction of stormwater intothe apparatus. The longitudinal spacing of the angled baffle(s) 220 ispreferably optimized to provide a minimum of one manhole 135 access forevery approximately 64 square feet of pollutant capture area forsubsequent collection and removal of sequestered sediment andhydrocarbon material via vacuum suction lift or mechanical means. In oneembodiment, the minimum size for the bypass manhole 400 is typicallyaround 36″ by 36″ square or, alternatively, 48″ inside diameter. Theretypically is a 30″ minimum spacing between the bypass manhole 400,outlet box 470 and the main tank 480 of the apparatus 100 to allowsufficient space for the installation and sealing of influent connectionpipes 180 and effluent connection pipes.

[0122] As known to one of ordinary skill in the art, the influentconnection pipes 180, effluent connection pipes 290, and bypass pipes430 are typically supplied and cut to proper length depending on thetopography, flow, and specific requirements of a particular site.Similarly, the dimensions of the apparatus will vary based on siterequirements.

[0123] The decant period or drain down time is optimized to allow forthe gravity separation of pollutants with either a specific gravity lessthan or greater than water. The retention time of the capture volume inthe stacked water column provides a quiescent period for enhancedsettling, and is consistent with recommendations shown in “Removal Ratevs. Detention Time for Stormwater Pollutants as defined in“Effectiveness of Extended Detention Ponds” authored by Grizzard et al.,1986 or other similar period recommendations as commonly known to thoseof skill in the art.

[0124] In one embodiment, the process capture volume stormwater flowrate is metered by a fixed aperture orifice 280 to insure properretention of the capture volume and regulate maximum discharge flowrate. In one embodiment, a flow control orifice may be, for example,mounted in a sealed outlet tee fitting with a standpipe 490 top rim atsuch elevation to prevent flow “short circuiting” at maximum waterlevels.

[0125] The orifice 280 is desirably protected from neutrally buoyantmaterial by a removal screen 270, which desirably typically includes aminimum net opening area of about 25 to 50 times the opening of theorifice, and preferably about 35 times the opening of the orifice. Theorifice 280, standpipe 490, and screen 270 are preferably constructed ofnon-metallic non-corrosive materials.

[0126]FIG. 10 provides an illustration of the apparatus, in oneembodiment, incorporating a dynamic flow control orifice.

[0127] Unlike previous devices, the dynamic flow control orifice system500 is a moveable orifice that differs from all other previous devices,as its primary purpose is to control the time for outflow of stormwaterfrom said stormwater mitigation system, by maintaining a constantdischarge rate throughout a majority of the discharge volume withoututilizing any outside mechanical or electrical force or power. Thedynamic flow control orifice system 500 does so by utilizing a properlysized and located orifice 510 within a buoyant floatation collar 520protected from surface contamination via a solid shield 530 and fromneutrally buoyant materials by a screen 540. A combination of gravityand buoyancy thus keeps the dynamic flow control orifice system at anadvantageous position in the apparatus without outside influence, whilethe height of the orifice 510 is adjustable relative to the watersurface by adjusting the vertical distance between the orifice 510 andthe flotation collar 520. The vertical adjustment of the orifice 510advantageously maintains the predetermined discharge flow rate throughthe great majority of retained capture volume. The action arm 550 istypically pivoted on a non-mechanical swing joint 560 to arc through theentire vertical range of the retained capture volume, and permits theorifice to move with the water level. By comparison, a fixed outletorifice 280 as shown in FIG. 9, for example, typically does not movewith the vault water level.

[0128] The preferred construction material for this component issynthetic hydrophobic material with non-corrosive fasteners, however,any suitable material such as plastic, fiberglass, and the like are tobe considered included within the description and application of thisapparatus. The simplified gravity dynamic flow control orifice describedpresently herein can advantageously be applied to any water treatmentsystem, including the embodiments described herein and other systemsknown to artisans of ordinary skill in the art.

[0129]FIG. 11 provides a detailed plan view of the apparatus, in oneembodiment, incorporating an integral overflow bypass structure. In oneembodiment, this stormwater treatment apparatus is an integrated systemwhereby the above mentioned bypass manhole 400, volume control weir 410and junction box 470 are combined and advantageously made integralwithin the confines of the stormwater treatment apparatus itself, as atypically unitary below grade modular precast concrete stormwatercontrol and treatment device that is designed to manage and treatstormwater runoff by diverting the design water quality capture volumeinto the apparatus as a surcharged detention storage volume defined asthe active pool and controlled release of said capture volume, withsediments stored in the permanent pool. The preferred constructionmaterial for all structural components is precast concrete however, anysuitable material such as plastic, fiberglass, steel, cast in placeconcrete, and the like are applicable to this apparatus.

[0130] The integral bypass structure apparatus utilizes a novel,properly sized integral weir appurtenance 410 to divert thepredetermined design capture volume water volume into the modularapparatus 100 from a stormwater collection system connected by, forexample, a collection system inflow pipe 184. This capture of thecapture volume is brought about by a integral volume control diversionweir 410 that directs the design runoff into the apparatus through theapparatus inflow pipe 180, with a minimum hydraulic loss into theapparatus 100. Any subsequent flow beyond that of the design capturevolume is allowed to bypass the apparatus 100 via the integral volumecontrol diversion weir 410 returning to the stormwater or runoffcollection system or receiving waters through a collection systemoutflow pipe 292. Stormwater treated by the apparatus is returned via adischarge pipe 280 to the combination junction box 470/bypass manhole400 for return to the stormwater or runoff collection system orreceiving waters through the collection system outflow pipe 292.

[0131] In one embodiment the integral bypass system is preferablyconfigured with the apparatus 100 aligned perpendicular to thecollection stormdrain that is to be intercepted. The bypass headworks isadvantageously configured to provide a minimum footprint, throughintegration of the bypass manhole 400 and junction box 470 with theentire apparatus, while allowing for a trash and debris collectionassembly to be incorporated into the integrated apparatus treatmenttrain. The size of the bypass headworks 400, junction 470 and integralweir 410 elevation relative to the apparatus is typically established bythe maximum design flow rate in the collection stormdrain that is to beintercepted. The headworks size typically corresponds to the minimumrequired for the integral weir 410 size, location and materials of thestormdrain main and inflow pipes 184. Depending on the topography of thestormwater collection system for which the apparatus 100 is going to beconnected, the position of the stormwater collection system inflow pipe184 and stormwater collection system outflow pipe 292 may beadvantageously altered and placed in different positions on the junctionbox 470/bypass manhole 400, as apparent to one of ordinary skill in theart, in order to minimize the footprint of the apparatus 100.

[0132] As would be apparent to one of ordinary skill in the art, theapparatus should typically be designed to withstand an AASHTO (“AmericanAssociation of State Highway and Transportation Officials”) or ASTM(“American Society for Testing and Materials”) C 890 H-20 trafficloading with 1.0′-6.0′ of earth cover. The apparatus is flexible and canbe designed to withstand other anticipated loads as designated by thesite engineer and specific site requirements.

[0133] To ensure acceptable hydraulic loading rates, promotion ofsettling and retention of pollutants, and enable proper maintenance, theminimum permanent pool liquid depth is typically between 1′ to 3′, orlarger for large embodiments of the apparatus. To provide a minimumhydraulic loading ratio in order to promote the settling of particlesfrom the stormwater flow, there is typically a minimum of approximatelyone square foot of surface area for about each about 60 gallons of totalliquid capacity.

[0134] The apparatus typically has a minimum of three access openingsfor maintenance, preferably at the inlet section, center section, andoutlet section, but the number of openings is foreseen to vary based onsite requirements. Openings typically have a minimum clear opening ofabout 30″ in diameter, and are typically located over each compartmentof the apparatus. There typically is an additional access opening forevery about 8′ of interception length in the center section of theapparatus. In one embodiment, there typically is an additional accessopening on the bypass manhole and outlet box.

[0135] The disclosed apparatus offers the designer and the developer anew degree of freedom in solving a large number of stormwater qualityproblem situations. Most existing structural stormwater treatmentsystems rely on a flow through rate calculation to size theirtechnologies, thereby not fully considering the hydraulic or waterquality impacts on the receiving waters. The method, as defined in“Urban Runoff Quality Management,” WEF Manual of Practice No. 23, andASCE Manual and Report on Engineering Practice No. 87, addresses theseconcerns. Those concerns have previously defied reasonable economicalsolutions using previously available structural stormwater mitigationsystems, but are advantageously resolved by the present apparatus.

[0136] This method may also be modified, as known to artisans ofordinary skill, for example, to allow sizing of the capture volume usingthe mean runoff volume as defined, for instance, by Discroll, et al.1989 and to accommodate an approximate recommended six hour drain downtime.

[0137] The capture volume stacked water column provides the mostefficient use of available system footprint. Owing to this feature, theapparatus typically requires a minimum of about three feet, andpreferably about five feet, of vertical temporary water storagecapacity, as apparent to artisans of ordinary skill. This temporarystacked water column is accomplished in the standard apparatusarrangements by use of a bypass weir sized to provide a minimum ofbackwater while insuring the full capture volume potential of theselected vault. Alternate system configurations accomplish the stackedwater column configuration by providing the necessary verticalseparation within the stormdrain piping system itself or by using apumped system. These systems can use, for example, an external bypass,an internal bypass, a surface bypass, pumped discharge, and/or a bypasswith a fall system.

[0138] As is typically known to those of skill in the art, the externalapparatus “bypass with weir” configuration is advantageously with thevault aligned parallel to and offset approximately three feet clear fromthe collection stormdrain that is to be intercepted. The bypass manholeis, in one embodiment, located approximately eight feet up gradient fromthe apparatus influent. The size of the bypass manhole and weirelevation relative to the apparatus is typically established by themaximum design flow rate in the collection stormdrain that is to beintercepted.

[0139] For example, in one embodiment, as familiar to one of skill inthe art, the influent pipe typically has a minimum of about 1% slope tothe apparatus, and is preferably constructed of SDR-35 PVC. The influentpipe typically exits the bypass manhole at about 45 degrees to thestormdrain flowline with, in one embodiment, a ⅛-turn elbow located nearthe apparatus. The effluent pipe is typically about 8″ SDR 35 PVC andhas a slope at about 1% from the apparatus to the junction box, sizedequivalent to the bypass manhole. The orifice operating head istypically calculated from the vault soffit to the springline of theeffluent pipe. Due to the fact that the apparatus operates with asurcharge water column, all pipe sizes and angles are based on smoothwall SDR 35 PVC pipe in order to advantageously provide a flexiblewatertight connections a all penetrations. However, other constructionsare also useable based on specific site conditions and requirements, asknown to artisans of ordinary skill in the art.

[0140] A junction box is, in one embodiment and as familiar to one ofskill in the art, approximately parallel, approximately 3 feet clearfrom the collection stormdrain, and approximately 8 feet down gradientfrom the apparatus effluent. The size of the junction box is establishedby the design flow rate in the collection stormdrain, maximum pipe sizepenetrations and relative piping angles, and is similar to thosetypically used for the “bypass manhole.”

[0141] The “bypass with fall” arrangement is similar to the standardconfiguration with regard to the bypass manhole, junction box andinfluent/effluent pipe sizes. However, the bypass manhole does notrequire a weir in this arrangement. The orifice operating head iscalculated from the vault soffit to the springline of the effluent pipe.

[0142] The “pumped discharge” arrangement is also similar to thestandard configuration with the bypass manhole, by-pass pipe elevationand junction box, except that the effluent is discharged through aduplex pump system uniquely designed to be contained within theapparatus or junction box.

[0143] The pump positive operating head is calculated from the vaultsoffit. The pump discharge rate is calculated based on the outflow rateform the apparatus.

[0144] The “surface by-pass” is unique in that because by definition theflowline of the storm drainage is on surface above the apparatus. Theorifice operating head is calculated from the surface hydraulic gradeline to the springline of the effluent pipe. While this arrangement doesnot require a dedicated bypass manhole or junction box it does require adrop inlet or catch basin at similar locations to the turning manholesas shown on the “overflow with weir” arrangement.

[0145] The preferred “standard internal bypass” configuration, as shownin FIG. 10, is with the vault aligned perpendicular to the collectionstormdrain that is to be intercepted. The bypass headworks is soconfigured to provide a minimum footprint while allowing for a trash anddebris collection assembly to be incorporated into the apparatustreatment train. The size of the bypass headworks and weir elevationrelative to the apparatus shall be established by the maximum designflow rate in the collection stormdrain that is to be intercepted. Theheadworks size corresponds to the minimum required for the size,location and materials of the stormdrain main and influent pipes. Theorifice operating head is calculated from the vault soffit to thespringline of the effluent pipe.

[0146] The description given herein describes particular embodiments ofthe present apparatus, and other embodiments are foreseen and includedherein and can be adapted by artisans of ordinary skill in the art, suchthat the present invention should be defined only by the followingclaims and equivalents thereof.

What is claimed is:
 1. A stormwater treatment apparatus, comprising: areceptacle adapted to receive water flowing from a surface drainagearea, comprising: the receptacle having a bottom wall and a top wall; aninlet, the inlet supplying water to the receptacle; an outlet, theoutlet passing water out of the receptacle; the inlet and the outletbeing in fluid communication with one another; a permanent pool, thepermanent pool defined by at least the bottom wall of the receptacle,and extending upward from said bottom wall to the height of said outlet,the permanent pool forming a region of reduced flow velocity to trapsediments therein; and, an inactive pool, the inactive pool defined byat least the permanent pool, a first baffle extending from the bottomwall, a second baffle extending from the bottom wall, and the bottomwall of the receptacle.
 2. The apparatus of claim 1, wherein thereceptacle additionally comprises an active pool, the active pooldefined by at least the top wall of the receptacle, and extendingdownward from said top wall to at least the height of said outlet. 3.The apparatus of claim 1, wherein the outlet includes an orificesubstantially smaller than the inlet.
 4. The apparatus of claim 1,wherein the apparatus includes an overflow structure, the overflowstructure diverting excess stormwater from the receptacle.
 5. Theapparatus of claim 4, wherein the overflow structure includes a controlweir and an apparatus inlet, and the overflow structure is integral withthe receptacle.
 6. The apparatus of claim 5, wherein the integraloverflow structure includes a stormwater collection inflow pipe and astormwater collection outflow pipe.
 7. The apparatus of claim 5, whereinthe integral overflow structure includes an apparatus outlet pipe, theapparatus outlet pipe returning water treated in the receptacle to theoverflow structure.
 8. The apparatus of claim 5, further comprising acontrol weir, the control weir regulating the diversion of water to thebypass pipe.
 9. A stormwater treatment apparatus, comprising: areceptacle adapted to receive water flowing from a surface drainagearea, the receptacle having at least a top and a bottom; an inletsection, the inlet section supplying water to the receptacle; an outletsection, the outlet section passing water out of the receptacle; atleast one mid section, the at least one mid section comprising a fluidcommunication between the inlet section and the outlet section; apermanent pool, the permanent pool defined by at least the bottom wallof the receptacle, and extending upward from said bottom wall to atleast the height of said outlet; the permanent pool generally below thepath of fluid communication; the permanent pool forming a region ofreduced flow velocity to trap sediments therein.
 10. The apparatus ofclaim 9, wherein the receptacle additionally comprises an inactive pool,the inactive pool defined by at least the permanent pool, a first baffleextending from the bottom of the receptacle, a second baffle extendingfrom the bottom of the receptacle, and the bottom of the receptacle. 11.The apparatus of claim 9, wherein the receptacle additionally comprisesan active pool, the active pool defined by at least the top wall of thereceptacle, and extending downward from said top wall to the height ofsaid outlet.
 12. The apparatus of claim 9, wherein at least a firstportion of the first baffle is at an angle of between about thirtydegrees and about sixty degrees with the bottom of the receptacle. 13.The apparatus of claim 9, wherein at least a first portion of the secondbaffle is at an angle of between thirty degrees and sixty degrees withthe bottom of the receptacle.
 14. The apparatus of claim 9, wherein atleast a first portion of the first baffle is at an angle of aboutforty-five degrees with the bottom of the receptacle.
 15. The apparatusof claim 9, wherein at least a first portion of the second baffle is atan angle of about forty-five degrees with the bottom of the receptacle.16. The apparatus of claim 12, wherein at least a second portion of thefirst baffle is at an angle of roughly ninety degrees with the bottom ofthe receptacle.
 17. The apparatus of claim 13, wherein at least a secondportion of the second baffle is at an angle of roughly ninety degreeswith the bottom of the receptacle.
 18. The apparatus of claim 9, whereinthe apparatus has a volume of at least 500 cubic feet.
 19. The apparatusof claim 9, additionally comprising: a third baffle, the third bafflenear said inlet, the third baffle extending down from the top wall ofthe receptacle; and, a fourth baffle, the fourth baffle near saidoutlet, the fourth baffle extending down from the top wall of thereceptacle.
 20. A stormwater treatment apparatus, comprising: areceptacle adapted to receive water flowing from a surface drainagearea; the receptacle having a bottom, a top, and a perimeter; thereceptacle having an inlet and an outlet; the inlet and the outlet beingin fluid communication with one another; an active pool, the active pooldefined by at least the top wall of the receptacle, the perimeter of thereceptacle, and extending downward from said top wall to at least theheight of said outlet, the active pool a region of fluid communicationbetween the inlet and the outlet; a permanent pool, the permanent pool aregion of little or no flow gravitationally beneath the active pool totrap sediments therein.
 21. The apparatus of claim 20, wherein theinactive pool is a region defined by at least a first baffle and asecond baffle, the perimeter of the receptacle, and the permanent pool.22. The apparatus of claim 20, wherein the outlet comprises an orifacesubstantially smaller than the inlet.
 23. The apparatus of claim 20,wherein the outlet includes an overflow structure, said overflowstructure diverting excess stormwater from said receptacle when saidreceptacle is at or near full, the overflow structure not substantiallyeffecting the performance of the active pool.
 24. The apparatus of claim23, wherein the overflow structure is integral to the receptacle, theintegral overflow structure additionally comprising: a control weir, astormwater collection system inflow, an apparatus inflow, and an accessway.
 25. The apparatus of claim 23, wherein the integral overflowstructure includes a stormwater collection inflow pipe and a stormwatercollection outflow pipe.
 26. The apparatus of claim 23, wherein theintegral overflow structure includes an apparatus outlet pipe, theapparatus outlet pipe returning water treated in the receptacle to theoverflow structure.
 27. A stormwater treatment apparatus, comprising: areceptacle adapted to receive water flowing from a surface drainagearea; the receptacle having a bottom, a top, and a perimeter; thereceptacle having an inlet and an outlet, the outlet including anoriface smaller than the inlet, the receptacle having an inlet, theinlet including an integral overflow structure, said overflow structurediverting excess stormwater from said receptacle when said receptacle isat or near fall; the inlet and the outlet being in fluid communicationwith one another; an active pool, the active pool is a region defined bythe top of the receptacle, the sides of the receptacle, and at least theheight of the outlet; a permanent pool, the permanent pool a region oflittle or no flow beneath the active pool to trap at least smallsediments therein; and, an inactive pool, the inactive pool a regiondefined by the permanent pool, at least a first baffle attached to thebottom of the receptacle, a second baffle attached to the bottom of thereceptacle, the sides of the receptacle, and the bottom of thereceptacle.
 28. The apparatus of claim 27, wherein at least a firstportion of the second baffle is at an angle of between thirty degreesand sixty degrees with the bottom of the receptacle.
 29. The apparatusof claim 27, wherein at least a first portion of the first baffle is atan angle of about forty-five degrees with the bottom of the receptacle.30. The apparatus of claim 27, wherein at least a first portion of thesecond baffle is at an angle of about forty-five degrees with the bottomof the receptacle.
 31. The apparatus of claim 29, wherein at least asecond portion of the first baffle is at an angle of roughly ninetydegrees with the bottom of the receptacle.
 32. The apparatus of claim30, wherein at least a second portion of the second baffle is at anangle of roughly ninety degrees with the bottom of the receptacle. 33.The apparatus of claim 27, wherein the apparatus has a volume of atleast 500 cubic feet.
 34. An apparatus for separation of pollutants inrunoff that are less and more dense than the runoff water, comprising: areceptacle adapted to receive stormwater runoff flowing from surfaceareas tributary to it, the receptacle having a bottom and a top, a leftside-wall and a right side-wall, and a front side-wall and endside-wall, forming a rectangular tank; an inlet for introducingstormwater flowing from tributary surface areas into the receptacle andan outlet for discharging water; at least four baffles positioned withinthe receptacle between the inlet and the outlet, with all of the bafflesattached to both sides of the receptacle, with at least two bafflesattached to the bottom of the receptacle and not attached to the top, atleast one baffle attached to the top of the receptacle and not attachedto the bottom, and at least one baffle that is not attached to thebottom and top of the receptacle; an inlet section for receiving water,for decreasing energy of the flowing water, and for uniformlydistributing water across the width of the receptacle; one or moremidsections for trapping materials more dense than water that settle outof water by gravity and for trapping materials less dense than waterthat rise to the surface of water by gravitational separation; an outletsection for discharging water at a controlled rate and for excludingmaterials more and less dense than water being discharged, the outletsection including an opening located on the end side-wall that allowswater in the apparatus to discharge, the outlet substantially smallerthan the inlet; a mesh screening, the mesh screening from the bottom tothe top of the apparatus is attached in a removable fashion to the endside-wall to form a barrier through which any water that dischargesthrough the opening must pass prior to discharge; an overflow structure,the overflow structure diverting excess stormwater flow from thereceptacle, the overflow structure integral with the receptacle; anactive pool, the active pool defined by at least the top wall of thereceptacle, and extending downward from said top wall to at least theheight of said outlet opening; a permanent pool, the permanent pooldefined by at least the bottom wall of the receptacle, and extendingupward to at least the height of said outlet opening; and, an inactivepool, the inactive pool defined by at least the permanent pool, thebottom of the receptacle, and the at least two baffles attached to thebottom of the receptacle.
 35. A stormwater treatment apparatus,comprising: a receptacle having a top, a bottom, a left side wall and aright side wall, an inlet side wall and an outlet end wall, saidreceptacle comprising an inlet section, an outlet section and at leastone midsection between said inlet section and said outlet section; aninlet located in said inlet section, spaced above said bottom; an outletlocated in said outlet section spaced above said bottom, said outletheight defining a permanent pool water surface elevation level; firstbaffle having an upstream side and a downstream side, said first baffleconnected to said bottom and extending upward no higher than saidpermanent pool water surface elevation level, said upstream side of saidfirst baffle including at least a portion angled upward from said bottomand towards said outlet; a second baffle between said first baffle andsaid outlet having an upstream side and a downstream side, said secondbaffle connected to said bottom and extending upward no higher than saidpermanent pool water surface elevation level, said upstream side of saidsecond baffle including at least a portion angled upward from saidbottom and toward said outlet; an active pool, said active pool definedby said inlet, said outlet, and said top of said receptacle; and, apermanent pool, said permanent pool defined by said first baffle, saidsecond baffle, said left side wall, said right side wall, and saidpermanent pool water surface elevation level, said permanent poolgenerally gravitationally below said active pool.
 36. A method forpurification and separation of a liquid, the method comprising:inputting the liquid into a receptacle through an inlet opening;interrupting the flow of the liquid around at least one inlet baffleafter the inlet opening; communicating the liquid through an active poolto an outlet opening, the outlet opening smaller than the intakeopening; interrupting the flow of the liquid around at least one outletbaffle before the outlet opening; settling sediments from the flow inthe active pool into at least one permanent pool, said permanent poolgravitationally below the active pool; and,
 37. The method of claim 36,further comprising the step of removing overflow liquid from thereceptacle when approximately full via an overflow structure.
 38. Themethod of claim 36, further comprising the step of placing the overflowstructure integral to the apparatus receptacle, and diverting excessflow over a control weir and back to a stormwater collection system. 39.A stormwater treatment apparatus, comprising: a receptacle adapted toreceive water flowing from a surface drainage area, comprising: thereceptacle having an inner wall and an outer wall; an inlet, the inletsupplying water to the receptacle; an outlet, the outlet passing waterout of the receptacle, the inlet and the outlet being in fluidcommunication with one another; and, a moveable orifice, the moveableorifice comprising an orifice, said orifice within a flotation collar,said orifice coupled to the outlet by an action arm.
 40. The apparatusof claim 39, wherein the moveable orifice additionally comprises a swingjoint, the swing joint pivoting the orifice.
 41. The apparatus of claim39, wherein the moveable orifice is composed of hydrophobic material andnon-corrosive fasteners.
 42. A moveable orifice for a stormwatertreatment system, the moveable orifice comprising: an orifice forreceiving water from a receptacle; a flotation collar, the flotationcollar coupled to the orifice; an action arm including a swing joint,the action arm pivoting the orifice within the receptacle; and, theorifice in fluid communication with an outlet of the receptacle.
 43. Theapparatus of claim 42, wherein the moveable orifice is composed ofhydrophobic material and non-corrosive fasteners.